Combustion engine pollution control

ABSTRACT

Procedure and apparatus have been developed for utilizing retained heat of hot exhaust gases being discharged from an internal combustion engine and for controlling the temperature of the gases to prevent damage to metal walls, maximize the oxidation of carbons and hydrocarbons, prevent the forming of nitrogen oxides, and promote the breakdown of nitrogen oxides formed in the engine, all before discharging the gases to the atmosphere. A jacketed manifold is employed in combination with a thermal reactor which receives exhaust gases in a central reaction chamber through a connecting venturi aspirator. The jacketing of the manifold is connected to draw-in ambient air into its vacuum space and to flow the air as heated by the manifold in a reverse flow path along the reaction chamber and thence into stages of the venturi aspirator to mix with and supply oxygen to the aspirator proportionately to the speed of operation or load demand of the engine, with the aspirator serving as means for providing a controlled intake of ambient air into the manifold.

United States Patent La Force [151 3,656,303 Apr. 18, 1972 [54] COMBUSTION ENGINE POLLUTION CONTROL [72] Inventor: Robert C. La Force, 514 West View Drive,

Beaver, Pa. 15009 22 Filed: Apr. 13,1970 21 App1.No.: 27,590

3,059,421 10/1962 Schnabel .60/30 3,168,806 2/1965 Calvert ..60/30 3,435,613 4/1969 Eannarino ..60/30 3 ,444,687 5/1969 Andersson ..60/30 3,460,916 8/1969 Aronsohn ..60/30 3,543,510 12/1970 Kaufmann ..60/3O Primary ExaminerDouglas Hart Attorney-Green, McCallister & Miller [57] ABSTRACT Procedure and apparatus have been developed for utilizing retained heat of hot exhaust gases being discharged from an internal combustion engine and for controlling the temperature of the gases to prevent damage to metal walls, maximize the oxidation of carbons and hydrocarbons, prevent the forming of nitrogen oxides, and promote the breakdown of nitrogen oxides formed in the engine, all before discharging the gases to the atmosphere. A jacketed manifold is employed in combination with a thermal reactor which receives exhaust gases in a central reaction chamber through a connecting venturi aspirator. The jacketing of the manifold is connected to draw-in ambient air into its vacuum space and to flow the air as heated by the manifold in a reverse flow path along the reaction chamber and thence into stages of the venturi aspirator to mix with and supply oxygen to the aspirator proportionately to the speed of operation or load demand of the engine, with the aspirator serving as means for providing a controlled intake of ambient air into the manifold.

12 Claims, 2 Drawing Figures PATENTEDAPR 18 {972 COMBUSTION ENGINE POLLUTION CONTROL The invention relates to an improved control of the temperature of exhaust gases from an internal combustion engine and particularly, to a simplified approach to the problem of minimizing air pollution by thermal reaction and without reaching manifold or reaction chamber temperatures that would normally damage metal retaining walls.

A phase of the invention deals with an improved approach to maximizing the oxidizing of carbon and hydrocarbons in engine exhaust gases while minimizing the nitric oxide content thereof for discharge downstream into the atmosphere. Another phase deals with providing air flow that is utilized for temperature control and that is supplied by a venturi to a reaction chamber.

In my copending U. S. Pat. application No. 856,027, filed Sept. 8, 1969, entitled Air Pollution System Temperature Control, the problem involved in the art has been outlined. Procedure and apparatus are disclosed that enable an effective maintenance of a reactive temperature of the gases before they are discharged to the atmosphere, and which employ valve means connected to jacketing for automatically varying heat transfer from a jacketed vessel through which exhaust gases are being flowed by varying the density of fluid within the jacketed portion of the vessel.

The present invention deals with an improved apparatus that is devised for maintaining the temperature of the exhaust gases in the chamber of a vessel or exhaust manifold within a requisite range and for introduction as by a venturi into a thermal reaction chamber. The venturi is sensitive to the velocity of the flow of exhaust gases from the manifold and is utilized to proportionately control the drawing-in of ambient air to cool the manifold and to supply the reaction chamber with reacting oxygen. The air thus drawn-in is first employed to cool the manifold and its gas content, and is then flowed within a jacket spacing or chamber about and along the reaction chamber to the discharge or downstream end thereof, then backwardly along a return pipe from a downstream towards an upstream end of the reaction chamber, and is finally introduced into stages of the venturi for introduction into the reaction chamber at the upstream end thereof. The purpose is to simplify the apparatus required and to, at the same time, maximize the conversion of the carbon and hydrocarbons into innocuous compounds while eliminating or at least minimizing the further formation of nitrogen oxides and, as an optimum, to break-down nitrogen oxides formed in the engine into nitrogen gas and oxygen and utilize nascent oxygen to further the reaction of the carbon and hydrocarbons.

An object of the invention has been to devise improved procedure and an apparatus system for maximizing the conversion of noxious compounds or fluids in the exhaust gas of an internal combustion engine into inert or innocuous gas or fluid.

Another object has been to eliminate limiting and complicating features of conventional exhaust treatment or noxious gas control systems and to devise procedure and an apparatus system which will be highly efficient in operation and, at the same time, will not require special temperature resistant metals for flow passageways, vessels, etc., through which the exhaust gases are passed or within which they are reacted.

Another object has been to provide an improved reaction type of procedure and apparatus for fluid or gas pollution control that automatically proportions the utilization of ambient air in accordance with the operation of an engine to increase the flow with an increase of speed and vice versa.

A further object of the invention has been to utilize flow of ambient air for cooling the walls of passageways of a vessel or manifold into and through which the exhaust gases are flowed and for preheating the air before using it in a reaction chamber.

A still further object of the invention has been to provide an efficient and practical approach to converging the noxious or poisonous gaseous content of combustion engine exhaust fluid discharge into a substantially innocuous or nonpoisonous content by subjecting a portion of the content to oxidation and another portion to reduction prior to discharge into the atmosphere.

These and other objects of the invention will appear to those skilled in the art from the illustrated embodiment.

In the drawings,

FIG. 1 is a top plan view, partially fragmented and sectioned, illustrating an apparatus system constructed and utilized in accordance with the invention.

FIG. 2 is a reduced view in elevation taken along a side of an internal combustion engine showing the construction and positioning of apparatus employed in accordance with the invention.

The invention employs an apparatus system or means which is sensitive to the flow or velocitymovement of hot exhaust gases from an internal combustion engine for supplying .cooling fluid to jacketing used along vessel means through which the gases flow. Temperature control is important from the standpoint of an exhaust manifold 15 and other parts whose temperature is to be maintained well below a temperature which may cause damage to cast iron or other conventional metal material used. Temperature control is also directly important from the standpoint of minimizing the noxious content of the exhaust gas or fluid that is to discharged to the atmosphere. The exhaust gas or fluid should be within a critical range of temperature and have sufficient oxygen supplied thereto for accomplishing a substantially full oxidation of its carbon and hydrocarbon content, to avoiding the formation of additional nitrogen oxides, and to further the reduction or breakdown of previously engine-formed noxious nitrogen oxides and provide free nitrogen and nascent oxygen available for reaction with the carbon and hydrocarbons. The operation is automatically controlled to supply ambient air and thus its oxygen content to a reaction chamber E in a proportional manner to the requirements of the reactions to be accom' plished therein and thus, proportionately to the supply of exhaust gases thereto.

Referring to the drawings, 10 represents a conventional gasoline-operated internal combustion engine block that is shown provided with an exhaust manifold 15 constructed in accordance with the invention and to which is connected a gas-sensitive flow aspirator means or venturi 30, and a reactor vessel or cylinder 34 having reaction chamber E through which exhaust gases move or flow before discharge through a conventional exhaust pipe system into the atmosphere. Referring particularly to FIG. 2, the manifold 15 which may be a metal casting or weldment has a main, cross-extending, flow, temperature-controlling and ambient air introducing chamber A which has end ports 16 and central ports 17 for receiving exhaust gases from combustion chambers of the engine block 10. The chamber A is connected at its inner ends to a centrally disposed exhaust header or chamber B from which exhaust gases flow downstream from the manifold 15 The front side or face as well as ends of the manifold 15 are of a dual-wall or jacketed construction to provide or define a pair of L-shaped temperature control and air flow chambers C. Ambient air. is introduced or flows into the chambers C through at least a pair of end-positioned through-extending short-length tubes 26 that provide inlet ports. To conserve heat during periods of idling speed or low load operation, the front side wall and end walls of the manifold 15 are shown covered or enclosed by a layer 27 of insulating material which may be of any suitable material, such as impregnated asbestos, resin impregnated fiber glass, etc. The insulating layer 27 will be mounted in any suitable manner, as by cementing or by clamping pieces. The back side wall of the manifold 15 also has a dual-wall construction to provide jacket spaces that are hermetically sealed. Two such jacket spaces 18 and 19 are illustrated which, in combination with an inset, backpositioned, insulating cover or enclosure layer 20, provide effective means for insulating the manifold 15 from the side wall of the engine block 10 on which it is mounted. The layer 20 insulating material may be of the same material as the front and side layer 27 and also may be secured in place in any suitable manner.

Reactor vessel or elongated cylinder 34 for conditioning the exhaust gases is shown connected to the header or exhaust chamber B of the manifold 15 through the agency of venturi 30. The reactor vessel 34 has an inner metal wall 35 defining longitudinally extending thermal reaction chamber E therealong. The venturi 30 has a primary stage tube or throat 31 and a secondary stage tube or throat 32 both of which deliver exhaust gases into a third or final stage venturi fluid delivery throat 33. It will be noted that the throats are of increasing radius or diameter from the upstream towards the downstream ends of the venturi 30. The upstream end of the venturi 30 is shown connected centrally to the manifold 15 and through an upstream converging end portion 35a of the inner wall 35 to the reaction chamber E. Entering fluids or gases flow along and are reacted in the chamber E to discharge through a downstream converging end portion 35b of the vessel wall 35 into an exhaust pipe 36. Oxygen-supplying air is introduced or aspirated into the venturi 30 for accomplishing oxidizing chemical reactions within the chamber E in a manner which will be hereinafter described. A jacket spacing F is shown provided about the venturi 30 which provides a dead air, insulative enclosure.

The reactor vessel 34 also has a radially, outwardly spaced outer metal wall 37 which surrounds the inner wall 35 and may be either formed integrally therewith as a casting or separately as a weldment, with its back and front end walls 38 and 39 being closed to define a jacket or heat transfer chamber D along the venturi 30 as well as the reaction chamber E. To conserve heat within the chambers D and E, a dual layer 40 of insulating material is shown covering or enclosing the outer reaches of the outer wall 37. This material may be of the same type mentioned in connection with the layers 20 and 27 of the manifold 15.

As shown in FIG. 2, the venturi 30 has a pair of sets or groups of radially extending aspirator tubes, one group 51 for its first stage throat 31, and a second group of tubes 52 for its second stage throat 32. The tubes 51 are supplied with air from a return flow, side-positioned and extending connector tube or pipe 45 that receives heated air from a downstream end of the jacket chamber or space E through a passageway defined by an inlet tube 47 and that delivers the air through a passageway defined by an outlet tube 49. Air is supplied to the upstream end of the heat transfer chamber D from chambers C through a group or pair of inlet tubes 28 that connect outlet, inner end portions of the chambers C at the upstream end of the vessel 34 to the chamber D.

The aspirator tube assembly 52 of the second stage throat 32 is supplied with air from a return-flow, side-mounted and extending, connector tube or pipe 46 that also receives heated air from the downstream end of the jacket chamber or space D through a passageway defined by an inlet tube 48, and that delivers the heated air to the assembly 52 through a passageway defined by an outlet tube 50. It will be noted that all of the aspirator tubes of the assembly 51 are connected at their outer ends to an annular head passageway 51a to which the inner end of the tube 49 is connected to deliver air thereto. Also, the outer ends of all of the tubes of the assembly 52 are connected to an annular head passageway 52a to which the inner end of the tube 50 is connected to deliver air thereto. It will thus be seen that air drawn in through ports 26 into the pair of L-shaped chambers C will first serve as a cooling medium for the manifold 15 as well as a heat pick-up medium, and will then serve as a temperature control flow medium along the chamber D for introduction into the two stages of venturi 30 by means of return flow piping 45 and 46. It will also be apparent that the flow engendered will depend for its effectiveness at a particular time upon negative pressure generated within the tube groups 51 and 52 of the venturi 30 which, in turn, is dependent upon the velocity of flow of exhaust gases through the venturi 30 from the manifold chamber B into the reaction chamber E.

The present system eliminates the disadvantageous features of an exhaust recirculating system which lessens the production of nitrogen oxides by lowering the temperature of the engine and thus, lowering the efficiency of its operation and increasing its fuel consumption. It also eliminates the elaborate means required for an after-buming system which tends to further the formation of nitrogen oxides and which requires forced air fed into an after-bumer and rather critical controls for maintaining the operation of the after-bumer for varied engine load conditions. Finally, the system of the invention eliminates the need for auxiliary powered means, such as an air pump, for providing a forced flow of exhaust gases, and the need for neutralizing chemicals or a catalyst. A catalyst is quickly contaminated with lead fuel and tends to disintegrate under the jolting operation of a vehicle and to lose its workability under excessive temperatures.

In accordance with the invention, a system is utilized which from the standpoint of its operation is substantially foolproof. It automatically controls a supply of an oxygen containing fluid, such as ambient air, for varying the heat insulating environment of the manifold and other parts of the system while, at the same time, conserves heat picked-up from the exhaust gases and utilizes it in the reaction chamber. lts oxygen content is employed in accomplishing desired reactions in the reaction chamber. The combustion engine with which the system is used may be operated at its maximum efficiency. The system provides a variable insulating action and utilizes an oxygen containing fluid or gas for oxidizing the carbon and hydrocarbon content of the exhaust gases into more or less inert or innocuous compounds and, at the same time, for preventing the fomiation of additional nitrogen oxides by an effective control of the range of temperature of the gases as utilized in the reaction chamber. The supply of oxygen to the chamber is proportioned in accordance with variable load requirements over operating range conditions of a combustion engine.

The venturi aspirator 30 as shown in FIG. 2, is also provided with an insulated construction in that its walls are jacketed by the dead air space or chamber F; its aspirating action is controlled by the speed of the exhaust gases and thus by the load on the engine. The venturi aspirator 30 in combination with the jacketing of the parts draws air into the system to both serve as a temperature control agency for maintaining the parts and the exhaust gases within a range of temperature that has been determined as a critical operating range from the standpoint of the reactions in the reactor vessel and that is below a maximum which will damage metal parts, such as the manifold. The venturi aspirator 30 accurately meters the air for such a purpose and, being controlled in its negative force application by the tube groups 51 and 52, proportions or draws in ambient air in accordance with the speed of the engine. Thus, the air intake may vary between about 5 cubic feet per hour for an idling operation of the engine to about l50 cubic feet per hour for maximum speed operation of the engine.

The greater the quantity of air being drawn in, the greater will be its density in the jacketed chambers or portions of the manifold 15 and the greater its ability to transfer or conduct heat from inner to outer wall portions of the manifold and dissipate it both by conduction and convection. The air density or flow in this sense serves as a variable insulation means so as to prevent the metal parts, such as those of the manifold wall, from becoming over-heated and so as to maintain or provide the gases within a range of temperature which is conducive to maximum reaction efficiency in the reactor vessel 34. The reaction vessel 34 is constructed and utilized to maintain the temperature of the gases during the reaction within its chamber E within a minimum of about l,00O F and a maximum of about 2,000 F, with an optimum range of operation being about 1,000 to 1,600 F.

It has been determined that within such a range of temperature and under the conditions of operation engendered by the system or apparatus herein disclosed, thai new and improved types of chemical reactions are accomplished within the reaction chamber. In this connection, the temperature is always maintained well below the 3,000 to 3,500 F at which the oxidation of nitrogen gas is greatly accelerated and at which an engine may be operating under fairly heavy load conditions. This is enabled by providing means to actively remove or dissipate heat from the exhaust gases when they are above 2,000 F, under higher load conditions, and to maintain their tem perature when the engine is operating under low load conditions and thus at lower temperatures below which effective oxidation of carbon and hydrocarbons cannot be effectively accomplished. It also has been discovered that within such a range of temperature, above indicated, the presence of the carbon and hydrocarbons that are not fully oxidized in the exhaust gas tends to further the breakdown of nitrogen oxides, to take nascent oxygen therefrom and utilize it in completing the desired full oxidation of them, as distinguished from the nitrogen gases.

There is very little dwell time of the gases within the reaction chamber E, since they move briskly therethrough at a rate depending on or proportionately to the speed of the engine. Thus, the conditions are not such as to promote the formation of nitrogen oxides near the higher limit of 2,000 E of the temperature range, as would occur if the gases were held for a considerable period of time at such temperature. It is also of interest to note that heat is given off in the reactions which involve oxidation of carbon or carbon monoxide into carbon dioxide as well as the oxidation of hydrocarbons, in the sense that the reactions areexothermic while, on the other hand, nitrogen oxides tend to be exothermic when they break down into their components with the reaction being endothermic from the standpoint of forming the oxides from nitrogen and oxygen. Also, it has been found that it is disadvantageous to cool the exhaust gases too quickly in the sense of a quenching operation, since this tends to fix the nitrogen oxides at about l,l F. Such a quenching is avoided by jacketing the manifold, the venturi and the reaction chamber E and by the use of insulating areas.

Incidentally, the size of the group or sets of venturi aspirator tubes 51 and 52 may be varied to provide a proper flow operation of the ambient air into and through the system in accordance with the criteria that has been previously set forth herein. Although a venturi has been found to produce optimum results in carrying out the invention, it will be apparent to those skilled in the art that suitable other means may be employed for controlling the introduction of air into the system such as a pump, although difficulty may be encountered in properly proportioning the flow in an automatic manner with the operation of the combustion engine. It will, however, be apparent to those skilled in the art that various modifications, changes, additions and adaptations may be made in connection with the disclosed apparatus to embody principles of the invention, either partially or fully, all within its scope.

As shown in FIG. 1, the centrally disposed chamber or area A and centrally disposed downstream chamber area or head portion B for the flow of hot exhaust gas are jacketed along the outside walls of the manifold 15, and fixed or inanimate insulating means 27 is applied to the walls externally of the jacketing of chamber C. Also, fixed or inanimate insulating means 40 is applied to walls of the reactor 34 externally of the jacketed chamber D thereof. Cooling fluid or air flow is provided along the jacketing of the manifold 15 that is proportioned to the BTUs or quantity of heat generated therein by the flow of hot exhaust gas therethrough. The cooling fluid leaves the downstream end or header portion B of the manifold 15 in a heated condition and is then introduced into the jacketing of the reactor 34 at the downstream end of its reaction chamber E and flows backwardly along and about the jacketing to an upstream end of the chamber and about the venturi 30 before it is introduced into the reaction chamber E through the venturi 30. In this manner, heat picked up by the cooling fluid is used to maintain the temperature of the manifold 15 below a maximum and assure that the exhaust gases leaving the manifold are within a desired range for introduction into the reaction chamber E. Also, the heat or BTUs picked up by the fluid is conserved by flowing it along the reactor 34, the venturi 30, and ultimately into the reaction chamber E. It will be apparent that the flow about the reaction chamber and the venturi will minimize any heat gradient between the outer walls and the ambient atmosphere. Although the temperature of the exhaust gases may not vary greatly between idling and full engine speeds, the quantity of heat will, in any event, depend on the rate of flow and the volume of flow.

I claim:

1. In a process for thermally reacting hot exhaust gases being produced by an internal combustion engine for minimizing noxious gas content thereof before discharge into the ambient atmosphere, flowing the hot exhaust gases from the engine through a jacketed manifold into and along a jacketed reaction chamber, maintaining the exhaust gases during their flow through the manifold into and along the reaction chamber within a temperature range that is conducive to the full oxidation of carbon and hydrocarbon content thereof and that is inhibitive of the oxidation of nitrogen gas content thereof, while introducing ambient air along the jacketing into the reaction chamber and promoting thermal reactions therein, introducing the ambient air into and moving it along the jacketing of the manifold and then into and along the jacketing of the reaction chamber, and finally into an upstream end of the reaction chamber at a rate proportioned to the rate of flow of the exhaust gases from the engine.

2. In a process as defined in claim 1, maintaining the temperature range by variably insulating; the manifold and the reaction chamber proportionately to the rate of movement of the hot exhaust gases flowing from the engine.

3. In a process as defined in claim 1, maintaining the temperature of the exhaust gases in the reaction chamber within a range of about 1,000 to 2,000 F.

4. In a process as defined in claim 1 wherein the rate of movementof the ambient air is automatically controlled by negative pressure generated by the flow introduction of the exhaust gases into an upstream end of the reaction chamber.

5. In a process as defined in claim 4, flowing exhaust gases from the manifold through a venturi into an upstream end of the reaction chamber, and aspirating ambient air from the jacketing of the reaction chamber into the upstream end thereof through the venturi.

6. In a process as defined in claim 5, flowing the ambient air from the jacketing of the manifold into an upstream end of the jacketing of the reaction chamber and therealong to a downstream end thereof, flowing the air from the downstream end of the jacketing of the reaction chamber into a throat area of the venturi and thence into the upstream end of the reaction chamber.

7. In a process as defined in claim 6, dividing the flow of air from the downstream end of the jacketing of the reaction chamber into at least two separate flow paths, and thereafter introducing the air from each flow path into upstreamdownstream spaced-apart portions of the throat area of the venturi.

8. In a process for thermally reacting hot exhaust gases being produced by an internal combustion engine for minimiz ing noxious gas content thereof before discharge into the ambient atmosphere, flowing hot exhaust gases from the engine through a jacketed manifold and downstream thereof into and along a jacketed reaction chamber, insulating the manifold externally of the jacketing thereof, applying and maintaining a cooling fluid flow along the jacketing that is proportioned to the quantity of heat generated in the manifold by the flow of hot exhaust gas therethrough, introducing heated fluid from the jacketing of the manifold into and along the jacketing of the reaction chamber and thereby limiting transfer of heat from the reaction chamber to the ambient atmosphere, introducing the heated fluid of the manifold into the jacketing of the reaction chamber downstream thereof, and flowing the heated fluid upstream along the reaction chamber to at least minimize the heat gradient between the reaction chamber and the ambient atmosphere.

9. In a process as defined in claim 8, ultimately introducing the heated fluid into and employing it in effecting reactions within the reaction chamber.

10. In a process as defined in claim 8, introducing the cooling fluid into the jacketing of the manifold from the ambient atmosphere proportionally to the rate of flow of exhaust gas from the manifold into the reaction chamber.

11. In apparatus for after-reacting hot exhaust gases being generated by an internal combustion engine to minimize the content of noxious gases and to maximize the content of innocuous gases, an exhaust manifold for mounting-connection to the engine for receiving the hot gases therefrom, said manifold having flow passage portions therein for receiving and conducting the exhaust gases therealong and having exhaust port means for flowing the exhaust gases therefrom, said manifold having jacketing about said flow passageway portions, inlet port means to said jacketing for introducing ambient air thereto, a reaction vessel defining a longitudinally extending reaction chamber therein and having jacketing about and along the reaction chamber, first means connecting the jacketing of said manifold to the jacketing of said reaction vessel, second means connecting said exhaust port means to an upstream end of the reaction chamber of said vessel for flowing exhaust gases from said manifold thereto, said second means having means for aspirating air from the jacketing of said reaction vessel into the exhaust gases being introduced into the upstream end of the reaction chamber, said second means being a venturi and having throat area portions connected to aspirate the ambient air from the jacketing of said reaction vessel and for drawing it through said inlet port means of said manifold proportionately to the rate of flow of the exhaust gases into the upstream end of the reaction chamber, said flow passage portions having a centrally disposed outlet head portion, said exhaust port means being connected to said head portion, and piping means connecting the downstream end of the jacketing of said reaction vessel to the throat area of said venturi for delivering the ambient air to said venturi.

12. In an apparatus as defined in claim 11, insulating means along said manifold externally of the jacketing thereof, and insulating means along said reaction vessel externally of the jacketing thereof. 

2. In a process as defined in claim 1, maintaining the temperature range by variably insulating the manifold and the reaction chamber proportionately to the rate of movement of the hot exhaust gases flowing from the engine.
 3. In a process as defined in claim 1, maintaining the temperature of the exhaust gases in the reaction chamber within a range of about 1,000* to 2,000* F.
 4. In a process as defined in claim 1 wherein the rate of movement of the ambient air is automatically controlled by negative pressure generated by the flow introduction of the exhaust gases into an upstream end of the reaction chamber.
 5. In a process as defined in claim 4, flowing exhaust gases from the manifold through a venturi into an upstream end of the reaction chamber, and aspirating ambient air from the jacketing of the reaction chamber into the upstream end thereof through the venturi.
 6. In a process as defined in claim 5, flowing the ambient air from the jacketing of the manifold into an upstream end of the jacketing of the reaction chamber and therealong to a downstream end thereof, flowing the air from the downstream end of the jacketing of the reaction chamber into a throat area of the venturi and thence into the upstream end of the reaction chamber.
 7. In a process as defined in claim 6, dividing the flow of air from the downstream end of the jacketing of the reaction chamber into at least two separate flow paths, and thereafter introducing the air from each flow path into upstream-downstream spaced-apart portions of the throat area of the venturi.
 8. In a process for thermally reacting hot exhaust gases being produced by an internal combustion engine for minimizing noxious gas content thereof before discharge into the ambient atmosphere, flowing hot exhaust gases from the engine through a jacketed manifold and downstream thereof into and along a jacketed reaction chamber, insulating the manifold externally of the jacketing thereof, applying and maintaining a cooling fluid flow along the jacketing that is proportioned to the quantity of heat generated in the manifold by the flow of hot exhaust gas therethrough, introducing heated fluid from the jacketing of the manifold into and along the jacketing of the reaction chamber and thereby limiting transfer of heat from the reaction chamber to the ambient atmosphere, introducing the heated fluid of the manifold into the jacketing of the reaction chamber downstream thereof, and flowing the heated fluid upstream along the reaction chamber to at least minimize the heat gradient between the reaction chamber and the ambient atmosphere.
 9. In a process as defined in claim 8, ultimately introducing the heated fluid into and employing it in effecting reactions within the reaction chamber.
 10. In a process as defined in claim 8, introducing the cooling fluid into the jacketing of the manifold from the ambient atmosphere proportionally to the rate of flow of exhaust gas from the manifold into the reaction chamber.
 11. In apparatus for after-reacting hot exhaust gases being generated by an internal combustion engine to minimize the content of noxious gases and to maximize the content of innocuous gases, an exhaust manifold for mounting-connection to the engine for receiving the hot gases therefrom, said manifold having flow passage portions therein for receiving and conducting the exhaust gases therealoNg and having exhaust port means for flowing the exhaust gases therefrom, said manifold having jacketing about said flow passageway portions, inlet port means to said jacketing for introducing ambient air thereto, a reaction vessel defining a longitudinally extending reaction chamber therein and having jacketing about and along the reaction chamber, first means connecting the jacketing of said manifold to the jacketing of said reaction vessel, second means connecting said exhaust port means to an upstream end of the reaction chamber of said vessel for flowing exhaust gases from said manifold thereto, said second means having means for aspirating air from the jacketing of said reaction vessel into the exhaust gases being introduced into the upstream end of the reaction chamber, said second means being a venturi and having throat area portions connected to aspirate the ambient air from the jacketing of said reaction vessel and for drawing it through said inlet port means of said manifold proportionately to the rate of flow of the exhaust gases into the upstream end of the reaction chamber, said flow passage portions having a centrally disposed outlet head portion, said exhaust port means being connected to said head portion, and piping means connecting the downstream end of the jacketing of said reaction vessel to the throat area of said venturi for delivering the ambient air to said venturi.
 12. In an apparatus as defined in claim 11, insulating means along said manifold externally of the jacketing thereof, and insulating means along said reaction vessel externally of the jacketing thereof. 